docs: def to_igraph(self, attribute="weight", **kwargs):
          """Convert to an igraph Graph
  
          Uses the igraph.Graph.Weighted_Adjacency constructor
  
          Parameters
          ----------
          attribute : str, optional (default: "weight")
          kwargs : additional arguments for igraph.Graph.Weighted_Adjacency
          """
          try:
              import igraph as ig
          except ImportError:
              raise ImportError("Please install igraph with "
                                "`pip install --user python-igraph`.")
          try:
              W = self.W
          except AttributeError:
              # not a pygsp graph
              W = self.K.copy()
              W = utils.set_diagonal(W, 0)
          return ig.Graph.Weighted_Adjacency(utils.to_dense(W).tolist(),
                                             attr=attribute, **kwargs)